Maybe it's for noise, maybe for smoother clutch operation, or both? Wet clutches don't rattle like a dry clutch? I assume my bike is a wet clutch?
I'm not sure how it works though, it must be stationary, it can't spin with the clutch assembly?
It does seem that part 10 attaches to it.
I know a bit, more about cars than bikes (I built a couple of rally cars in my youth) but assuming it is a wet clutch, part 10 is never going to hold oil in, there is no gasket or o ring, it really does look like it is just a push fit, bit I don't really want to pull or lever the old one off when I have no idea what I am dealing with.